1 / 9

Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas EMC ANALYSIS

Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas EMC ANALYSIS PM#03 Torino - April 5th- 6th, 2006. CAN Bus. El. & Az Motors Encoders. CAN Bus. 1kHz. ACU. ABM. EMC Self-compatibility ALMA ANTENNA ARCHITECTURE

stevie
Download Presentation

Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas EMC ANALYSIS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas • EMC ANALYSIS • PM#03 Torino - April 5th- 6th, 2006

  2. CAN Bus El. & Az Motors Encoders CAN Bus 1kHz ACU ABM • EMC Self-compatibility • ALMA ANTENNA ARCHITECTURE • ACU communicates with ABM and El. & Az. Motors by CAN BUS • CAN BUS Characteristics • The CAN bus is a balanced (differential) 2-wire interface running over either a Twisted Shielded Pair (TSP), Twisted Pair (TP), or Ribbon cable; • Impedance: 124Ohm termination (between + and – terminals)

  3. EMC Self-compatibility • IEC-61000-4-3 Standard (Radiated Radio-Frequency Electromagnetic Field Immunity Test) • The EMC Standard defines the radiated immunity test for ALMA electric / electronic equipments. The incident Electric Field Level is of 10V/m on the Equipment Under Test (EUT). • EMC Model (COMMON MODE) • INPUTS • A ribbon wire on ground plane • AWG24 cable, length 10m • Parametric analysis: h=1cm and 5cm (W.C.) • An incident electromagnetic wave with the • electric field of amplitude 20 V/m • Zs=10 Ohm//50nF • Zload=124 Ohm + common mode impedance

  4. EMC Self-compatibility • EMC Model (COMMON MODE) • Results • A maximum of 1.4V is expected from our • analysis as differential voltage on Zload • impedance. • The ISO 11898−2 specification (CAN spec.) • lists a common mode voltage specification • of −2.0 V (on CAN_L) to +7.0 V (on CAN_H) • for the data lines. • Conclusion • The estimated coupled voltage is of the same order of magnitude of common mode • noise that the CAN BUS can manage. It is better to reduce the coupled voltage using • TP or TSP cable.

  5. EMC Self-compatibility • CABIN RECIVE SHIELDING – ALMA REQUIREMENTS • The measured shielding effectiveness shall be 20dB at 12GHz. • Proposal Design • The shielding of the receiver cabin is achieved through: • Walls (aluminum on CFRP); • Roof (aluminum on CFRP); • Floor (steel on CFRP); • Cabin door (aluminum on CFRP); • The inner walls of the receiver cabin shall be an effective continuous metal surface for RFI shielding and RFI shielding continuity shall be provided on the door. • Considerations • Electric field coupling is often insignificant when well-shielded enclosures are used. • Magnetic field coupling is more serious problem: it can penetrate by diffusion, apertures and conductive penetrations.

  6. EMC Self-compatibility Current Diffusion Definition of “skin depth - ”: it is the point where these fields are reduced by a factor of 1/e (~ 0.37) In table is reported the SE considering a metallic barrier with thickness T= 10μm and an infinite surface. Conductive Penetrations (only for information) Wires and Tubing have not to enter inside the enclosure in order to avoid Antenna effects, as for picture on the right. The shield has to be connected on the external face of the case.

  7. EMC Self-compatibility • SUMMARY • The CAN BUS (but it could be generalized of each lines) has to use TP if is important to prevent coupling with magnetic field but it is better to use a TSP if a shielded barrier must be crossed. • Each wire, which has to cross a shield, has to present an overall shield if a consistent shielding effectiveness is required. • A pig-tail connection must be avoid. • The shield has to connected to the ground on both sides of the terminations. • Shields have not to be used intentionally as return lines for power and signal with exception of the RF coax lines.

  8. EMC - LEMP Analysis Reference Standard:IEC-61312-1 The IEC-61312-1 Standard considers two stroke: first and subsequent stroke. For both currents the following parameter are provided: The subsequent stroke is the quickest but the first stroke have a more important energy. • EMC MODEL – BIOT-SAVART LAW • The Biot-Savart law permits to calculate the magnetic field produced by a steady state current at a distant s (0.5m in our analysis) from the straight wire. • A shielding effectiveness of 40dB was • considered for Receiver Cabin.

  9. EMC - LEMP Analysis Conclusion: In figure is reported the estimated magnetic field at 50cm from the straight wire, produced by a lightning event (with a shield effectiveness of 40dB) it is mandatory that each electric/electronic supplier provides an accurate analysis/assessment/test which confirms that no problems are encountered when the equipment is subjected to the magnetic field reported in figure.

More Related